In the United States and Europe, it became Nintendo's fastest-selling Super Mario game ever, with 1.1 million copies sold in the US within five days.[120][121] According to the NPD Group, the game was the best-selling video game of October 2017,[122] and was listed by Amazon as the online retailer's highest-selling game of the year.[123]
I suspect it just got overshadowed by Zelda Breath of the Wild, which really stole the show for the Switch launch year.
Edit: Trying to think which Mario game was NOT considered a success? Maybe Mario Sunshine? That goes back to the Gamecube, and looking at it now... that ALSO had good reviews. I don't think there's been a dud in the mainline Mario franchise... ever?
People really love to hate on SMB2 (NES).
There is still a lot of desire for games you can play with people at a party, or play with your children and spouse all together on the same screen. Every other videogame maker has abandoned that niche.
Nintendo has never and probably will never try and seriously compete in the multiplayer arena - they've got some casual multiplayer stuff but they're not trying to out compete Call of Duty, Halo or Starcraft.
I do agree that they do milk those main properties for all their worth, but they're pretty careful about releasing bombs - Mario Odyssey was a pretty notable and dramatic fail for them but, again, the fact that their games suck to you doesn't matter. I'm a big fan of EU4 and as such Nintendo doesn't want my business - they cater to young and casual audiences building easy to access for the family games rather than historical simulators or Dark Souls.